Light-emitting device

ABSTRACT

An edge-emitting type light-emitting device ( 11000, 14000 ) comprises an organic light-emitting layer ( 40 ), a pair of electrode layers ( 30 ) and ( 50 ) for applying an electric field to the organic light-emitting layer ( 40 ), and an optical waveguide which transmits light emitted from the organic light-emitting layer ( 40 ) to the edge. The optical waveguide comprises a core layer ( 20 ) mainly transmitting light, and cladding layers ( 10 ) and ( 60 ) having a refractive index lower than that of the ecore layer ( 20 ). The core layer ( 20 ) may be a layer different from the organic light-emitting layer ( 40 ) or may comprise the organic light-emitting layer. A grating ( 12 ) is formed in the core layer ( 20 ) or in the boundary area between the core layer ( 20 ) and the cladding layer ( 10 ). A light-emitting device ( 31000 ) may comprise an optical fibre section ( 200 ). Another embodiment ( 43000 ) may comprise a defect and a grating having a one-dimensional periodic refractive index distribution and constituting a photonic band gap.

TECHNICAL FIELD

The present invention relates to a light-emitting device utilizingelectroluminescence (EL).

BACKGROUND OF ART

Semiconductor lasers have been used as a light source for an opticalcommunication system. Semiconductor lasers excel in wavelengthselectivity and are capable of emitting light with a single mode.However, semiconductor lasers require many stages of crystal growth andare difficult to manufacture. Another problem with semiconductor lasersis the limitation to the types of light-emitting materials which can beused. This restricts the wavelength of light which can be emitted bysemiconductor lasers.

Conventional EL light-emitting devices can emit light with a wavelengthhaving a broad spectral width and have been applied to displays and thelike. However, such EL light-emitting devices are unfit for applicationto optical communications and the like which require light with a narrowspectral width.

DISCLOSURE OF INVENTION

An object of the present invention is to provide a light-emitting devicewhich can emit light with a wavelength having a remarkably narrowspectral width in comparison with conventional EL light-emittingdevices, exhibits directivity, and can be applied to not only displaysbut also optical communications and the like.

A light-emitting device according to the present invention comprises:

a light-emitting layer being capable of emitting light byelectroluminescence;

a pair of electrode layers for applying an electric field to thelight-emitting layer; and

an optical waveguide for transmitting light emitted from thelight-emitting layer,

wherein a grating is formed in the optical waveguide.

According to this light-emitting device, electrons and holes areintroduced into the light-emitting layer respectively from the pair ofelectrode layers (cathode and anode). Light is emitted when themolecules return to the ground state from the excited state byrecombination of the electrons and holes in the light-emitting layer.The light emitted from the light-emitting layer is provided withwavelength selectivity and directivity by the grating formed in theoptical waveguide, specifically, a grating with alternating two mediumlayers each of which has a different refractive index arrangedperiodically.

It is preferable that the grating be a distributed feedback type ordistributed Bragg reflection-type grating. Such a distributed feedbacktype or distributed Bragg reflection-type grating causes the lightemitted from the light-emitting layer to resonate. As a result, lighthaving wavelength selectivity, a narrow emission spectral width, andexcellent directivity can be obtained. The pitch and depth of thegrating are designed depending on the wavelength of the light to beemitted.

Light can be emitted with a single mode by providing the distributedfeedback type grating with a λ/4 phase shifted structure or again-coupled structure. “λ” used herein indicates the wavelength of thelight inside the optical waveguide.

A grating of a distributed feedback type having a λ/4 phase shiftedstructure or a gain-coupled structure is a preferable configurationcommon to the light-emitting devices of the present invention. It issufficient for the grating to achieve the above functions. The gratingmay be formed in any layers constituting the optical waveguide.

It is preferable that the light-emitting layer comprises organiclight-emitting materials. Use of organic light-emitting materialsexpands selection of the materials and enables emission of light havingvarious wavelengths in comparison with the case using a semiconductor orinorganic materials.

The aspects described below from (a) to (d) can be given as examples ofsuch a light-emitting device.

(a) In a first aspect of the light-emitting device, the opticalwaveguide comprises a core layer mainly transmitting light, and acladding layer having a refractive index lower than the refractive indexof the core layer; and

the core layer comprises a layer which is different from thelight-emitting layer.

A feature of this light-emitting device is that the core layer, whichthe light transmits mainly, is formed from a layer different from thelight-emitting layer. The core layer is preferably made from materialshaving a refractive index higher than that of the light-emitting layer.This refractive index relationship ensures efficient introduction of thelight emitted from the light-emitting layer into the core layer. Thegrating may be formed in the core layer. The grating may be formed inthe boundary area between the cladding layer and a layer in contact withthe cladding layer such as the core layer.

In the case where the light-emitting layer is an organic light-emittinglayer comprising organic materials, the core layer may serve not only asa light transmitting layer, but also as at least one of a hole transportlayer, electron transport layer, transparent electrode layer, and thelike. The cladding layer is designed to have a refractive index lowerthan that of the core layer. The cladding layer may serve not only as alayer for light confinement, but also as an electrode layer, substrate,hole transport layer, electron transport layer, and the like.

(b) In a second aspect of the light-emitting device, the opticalwaveguide comprises a core layer mainly transmitting light, and acladding layer having a refractive index lower than the refractive indexof the core layer; and

the core layer comprises a layer including the light-emitting layer, and

the grating is formed in the optical waveguide.

A feature of this light-emitting device is that the light-emitting layeris included in the core layer which is the main light transmittinglayer. The grating may be formed in the core layer. The grating may alsobe formed in a boundary area between the cladding layer and a layer incontact with the cladding layer, such as the core layer. In thislight-emitting device, the light-emitting layer may be formedcontinuously or discontinuously one after another.

In the case where the light-emitting layer is an organic light-emittinglayer formed by organic light-emitting materials, the core layer mayfurther comprise at least one of a hole transport layer, an electrontransport layer, a transparent electrode layer, and the like. Thecladding layer may be designed to have a refractive index lower thanthat of the core layer. The cladding layer may serve not only as a layerfor light confinement, but also as an electrode layer, a substrate, anhole transport layer, an electron transport layer, and the like.

In the light-emitting device according to this aspect, the grating maybe formed by the light-emitting layer and a layer in contact with thelight-emitting layer. According to the device having such aconfiguration, light emitted from the light-emitting layer resonatesdirectly by the grating in the region including the light-emittinglayer. As a result, light is emitted with a selected wavelength andexcellent directivity.

(c) The light-emitting device as a third aspect of the present inventioncomprises an optical fiber section formed in one body,

wherein the optical fiber section comprises a core layer and a claddinglayer, and

wherein the optical waveguide is formed continuously with at least oneof the core layer or the cladding layer of the optical fiber section.

In this light-emitting device, because at least either the core layer orthe cladding layer of the optical fiber section is formed in one bodywaveguide, light having excellent wavelength selectivity and directivitycan be emitted from the light-emitting layer in the optical waveguideand supplied to the transmission system with high efficiency.

In this light-emitting device, the light-emitting layer may be includedin the optical waveguide. The optical waveguide may be either continuouswith the core layer of the optical fiber section or formed separatelywhile being optically connected. Furthermore, it is preferable that theoptical waveguide comprises a core-layer-continuing portion whichcontinues from the core layer of the optical fiber section. In the casewhere the optical waveguide comprises such a part, light output from theoptical waveguide is transmitted to the optical fiber with highefficiency. Moreover, this highly efficient optical combination can beobtained without requiring a delicate optical adjustment.

(d) In a fourth aspect of the light-emitting device, the grating has adefect and a one-dimensional periodic refractive index distributionwhich constitutes a photonic band gap; and

the defect is designed so that the energy level caused by the vacancy iswithin a specific emission spectrum.

According to this light-emitting device, electrons and holes areintroduced into the light-emitting layer respectively from a pair ofelectrode layers (cathode and anode). Light is emitted when themolecules return to the ground state from the excited state byrecombination of the electrons and holes in the light-emitting layer. Atthis time, light with a wavelength equivalent to the photonic band gapof the grating cannot be transmitted through the grating. Only the lightwith a wavelength equivalent to the energy level caused by the vacancycan be transmitted through the grating. Therefore, light with aremarkably narrow emission spectral width can be obtained with highefficiency by prescribing the width of the energy level caused by thevacancy.

A special feature of this aspect is in the structure of the grating.Specifically, the grating has the defect and the one-dimensionalperiodic refractive index distribution which constitutes the photonicband gap.

In this aspect, in order to confine the light and guide it in a certaindirection, the grating is preferably formed in the optical waveguidecomprising areas having either a high refractive index or low refractiveindex. For example, substrates, materials in contact with the grating orthe air layer can function as the cladding layer.

In the light-emitting device according to this aspect, thelight-emitting layer and the defect of the grating may have thefollowing configuration.

(1) The light-emitting layer formed in the defect also functions as thedefect.

(2) The light-emitting layer also functions as at least part of thedefect and the grating.

(3) The light-emitting layer is formed in a region different from thedefect.

In this aspect, the light-emitting layer is preferably comprises anorganic light-emitting layer formed by organic material. Use of such anorganic light-emitting layer is preferred to the photonic band gap usingsemiconductors due to the following reasons. A grating comprising anorganic light-emitting layer which constitutes a photonic band gap isnot affected by the irregular state of the boundary area of thelight-emitting layer and impurities in comparison with the case of usingsemiconductors, whereby excellent characteristics from the photonic bandgap can be obtained. Furthermore, in the case of forming a medium layerfrom an organic light-emitting layer, the manufacture becomes easy and agood periodic structure with a refractive index can be easily obtained,whereby superior characteristics from the photonic band gap can beobtained.

Some of the materials which can be used for forming each section of thelight-emitting device according to the present invention will beillustrated below. These materials are only some of the conventionalmaterials. Materials other than these materials can also be used.

(Light-emitting Layer)

Materials for the light-emitting layer are selected from conventionalcompounds to obtain light with a prescribed wavelength. Any of organicand inorganic compounds may be used as the materials for thelight-emitting layer. It is preferable to use organic compounds from theviewpoint of a wide variety of compounds and film-formability.

As examples of such organic compounds, aromatic diamine derivatives(TPD), oxydiazole derivatives (PBD), oxydiazole dimers (OXD-8),distyrarylene derivatives (DSA), beryllium-benzoquinolinol complex(Bebq), triphenylamine derivatives (MTDATA), rubrene, quinacridone,triazole derivatives, polyphenylene, polyalkylfluorene,polyalkylthiophene, azomethine zinc complex, polyphyrin zinc complex,benzooxazole zinc complex, and phenanthroline europium complex which aredisclosed in Japanese Patent Application Laid-open No. 10-153967 can begiven.

Specific examples of materials for the organic light-emitting layerinclude compounds disclosed in Japanese Patent Application Laid-open No.63-70257, No. 63-175860, No. 2-135361, No. 2-135359, No. 2-152184, No.8-248276 and No. 10-153967. These compounds can be used eitherindividually or in combinations of two or more.

As examples of inorganic compounds, ZnS:Mn (red region), ZnS:TbOF (greenregion), SrS:Cu, SrS:Ag, SrS:Ce (blue region), and the like can begiven.

(Optical Waveguide)

The optical waveguide comprises a core layer and a cladding layer havinga refractive index lower than that of the core layer. Conventionalinorganic and organic materials can be used for the core layer andcladding layer.

Typical examples of inorganic materials include TiO₂, TiO₂—SiO₂ mixture,ZnO, Nb₂O₅, Si₃N₄, Ta₂O₅, HfO₂, and ZrO₂ disclosed in Japanese PatentApplication Laid-open No. 5-273427.

Typical examples of organic materials include various conventionalresins such as thermoplastic resins, thermosetting resins, andphotocurable resins. These resins are appropriately selected dependingon a method of forming layers and the like. For example, in the case ofusing a resin which can be cured by energy of at least either heat orlight, commonly used exposure devices, baking ovens, hot plates, and thelike can be utilized.

As examples of such materials, a UV-curable resin disclosed in JapanesePatent Application No. 10-279439 applied by the applicant of the presentinvention can be given. Acrylic resins are suitable as such a UV-curableresins. UV-curable acrylic resins having excellent transparency andcapable of being cured in a short period of time can be produced usingvarious commercially-available resins and photosensitizers.

As specific examples of basic components of such UV-curable acrylicresins, prepolymers, oligomers, and monomers can be given.

Examples of prepolymers or oligomers include acrylates such as epoxyacrylates, urethane acrylates, polyester acrylates, polyether acrylates,and spiroacetal-type acrylates, methacrylates such as epoxymethacrylates, urethane methacrylates, polyester methacrylates, andpolyether methacrylates, and the like.

Examples of monomers include monofunctional monomers such as2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 2-hydroxyethylacrylate, 2-hydroxyethyl methacrylate, N-vinyl-2-pyrrolidone, carbitolacrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate,dicyclopentenyl acrylate, and 1,3-butanediol acrylate, bifunctionalmonomers such as 1,6-hexanediol diacrylate, 1,6-hexanedioldimethacrylate, neopentyl glycol diacrylate, neopentyl glycoldimethacrylate, ethylene glycol diacrylate, polyethylene glycoldiacrylate, and pentaerythritol diacrylate, and polyfunctional monomerssuch as trimethylolpropane triacrylate, trimethylolpropanetrimethacrylate, pentaerythritol triacrylate, and dipentaerythritolhexaacrylate.

The above examples of inorganic and organic materials are illustratedonly in consideration of light confinement. In the case where at leastone layer among the light-emitting layer, hole transport layer, electrontransport layer, and electrode layer functions as the core layer or thecladding layer, materials constituting these layers can be employed asmaterials for forming the core layer or the cladding layer constitutingthe optical waveguide.

(Hole Transport Layer)

As materials for the hole transport layer which is optionally formed,materials conventionally used as hole injection materials forphotoconductive materials or a hole injection layer for organiclight-emitting devices can be selectively used. As the materials for thehole transport layer, any organic or inorganic materials which have afunction of either hole introduction or electron barrier characteristicsare used. Materials disclosed in Japanese patent Application Laid-openNo. 248276/1996 can be given as specific examples of such materials.

(Electron Transport Layer)

Materials for the electron transport layer which is optionally formedare required to transport electrons introduced from the cathode to theorganic light-emitting layer and can be selected from conventionalmaterials. Materials disclosed in Japanese Patent Application Laid-openNo. 248276/1996 can be given as specific examples of such substances.

(Electrode Layer)

As the cathode, electron injectable metals, alloys, electricallyconductive compounds with a small work function (for example, 4 eV orless), or mixtures thereof can be used. Materials disclosed in JapanesePatent Application Laid-open No. 248276/1996 can be given as specificexamples of such electrode materials.

As the anode, metals, alloys, electrically conductive compounds with alarge work function (for example, 4 eV or more), or mixtures thereof canbe used. In the case of using optically transparent materials as theanode, transparent conductive materials such as CuI, ITO, SnO₂, and ZnOcan be used. In the case where transparency is not necessary, metalssuch as gold can be used.

In the present invention, the grating can be formed by conventionalmethods without specific limitations.

Typical examples of such methods are given below.

1) Lithographic Method

In this method, a positive or negative resist is irradiated withultraviolet rays, X-rays, or the like. The resist layer is patterned bydevelopment to form a grating. As a patterning technology using apolymethyl methacrylate resist or a novolak resin resist, for example,technologies disclosed in Japanese Patent Applications Laid-open No.6-224115 and No. 7-20637 can be given.

As a technology of patterning polyimide by photolithography, forexample, technologies disclosed in Japanese Patent ApplicationsLaid-open No. 7-181689 and No. 1-221741 can be given. Furthermore,Japanese Patent Application Laid-open No. 10-59743 discloses atechnology of forming a grating of polymethyl methacrylate or titaniumoxide on a glass substrate utilizing laser ablation.

2) Formation of Refractive Index Distribution by Irradiation

In this method, the optical waveguide section of the optical waveguideis irradiated with light having a wavelength which produces changes inthe refractive index to periodically form areas having differentrefractive indices on the optical waveguide section, thereby forming agrating. As such a method, it is preferable to form a grating by forminga layer of polymers or polymer precursors and polymerizing part of thepolymer layer by irradiation or the like to periodically form areashaving a different refractive index. Such a technology is disclosed inJapanese Patent Applications Laid-open No. 9-311238, No. 9-178901, No.8-15506, No. 5-297202, No. 5-32523, No. 5-39480, No. 9-211728, No.10-26702, No. 10-8300, and No. 2-51101.

3) Stamping Method

A grating is formed by, for example, hot stamping using a thermoplasticresin (Japanese Patent Application Laid-open No. 6-201907), stampingusing a UV curable resin (Japanese Patent Application Laid-open No.10-279439), or stamping using an electron-beam curable resin (JapanesePatent Application Laid-open No. 7-235075).

4) Etching Method

A thin film is selectively patterned using lithography and etchingtechnologies to form a grating.

Methods of forming a grating is described above. A grating consists oftwo areas each of which has a different refractive index. Such a gratingcan be formed by forming such two areas from two materials havingdifferent refractive indices, by partially modifying one material toform two areas having different refractive indices, and the like.

Each layer of the light-emitting device can be formed by a conventionalmethod. For example, the light-emitting layer is formed by a suitablefilm-forming method depending on the materials. A vapor depositionmethod, spin coating method, LB method, ink jet method, and the like canbe given as specific examples.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic oblique view of an organic light-emitting deviceaccording to a first embodiment of the present invention.

FIG. 1B is a cross-sectional view along the line A—A in FIG. 1A.

FIG. 2 is a cross-sectional view schematically showing an organiclight-emitting device according to a second embodiment of the presentinvention.

FIG. 3 is a cross-sectional view schematically showing an organiclight-emitting device according to a third embodiment of the presentinvention.

FIG. 4 is a cross-sectional view schematically showing an organiclight-emitting device according to a fourth embodiment of the presentinvention.

FIG. 5 is a cross-sectional view schematically showing an organiclight-emitting device according to a fifth embodiment of the presentinvention.

FIG. 6 is a cross-sectional view schematically showing an organiclight-emitting device according to a sixth embodiment of the presentinvention.

FIG. 7 is a cross-sectional view schematically showing modification ofan organic light-emitting device according to a sixth embodiment of thepresent invention.

FIG. 8 is a cross-sectional view schematically showing an organiclight-emitting device according to a seventh embodiment of the presentinvention.

FIG. 9 is a cross-sectional view schematically showing an organiclight-emitting device according to a eighth embodiment of the presentinvention.

FIG. 10 is a cross-sectional view schematically showing an organiclight-emitting device according to a ninth embodiment of the presentinvention.

FIG. 11 is a cross-sectional view schematically showing an organiclight-emitting device according to a tenth embodiment of the presentinvention.

FIG. 12 is a cross-sectional view schematically showing a light-emittingdevice according to an eleventh embodiment of the present invention.

FIG. 13 is a schematic cross-section viewed along the line B—B in FIG.12.

FIG. 14 is a schematic vertical section of a light-emitting deviceaccording to an twelfth embodiment of the present invention.

FIG. 15 is a schematic cross-section viewed along the line D—D in FIG.14.

FIG. 16 is a schematic vertical section of a light-emitting deviceaccording to an thirteenth embodiment of the present invention.

FIG. 17 is a schematic cross-section viewed along the line F—F in FIG.16.

FIG. 18 is a cross-sectional view schematically showing a light-emittingdevice according to a fourteenth embodiment of the present invention.

FIG. 19 is a schematic cross-section viewed along the line H—H in FIG.18.

FIG. 20 is a cross-sectional view schematically showing a light-emittingdevice according to a fifteenth embodiment of the present invention.

FIG. 21 is a cross-sectional view schematically showing a light-emittingdevice according to a sixteenth embodiment of the present invention.

FIG. 22 is a cross-sectional view schematically showing a light-emittingdevice according to a seventeenth embodiment of the present invention.

FIG. 23 is a cross-sectional view schematically showing a light-emittingdevice according to a eighteenth embodiment of the present invention.

FIG. 24 is a cross-sectional view schematically showing a light-emittingdevice according to a nineteenth embodiment of the present invention.

FIG. 25 is a cross-sectional view schematically showing a light-emittingdevice according to a twentieth embodiment of the present invention.

FIG. 26 is a cross-sectional view schematically showing a light-emittingdevice according to a twenty-first embodiment of the present invention.

FIG. 27 is a cross-sectional view schematically showing a light-emittingdevice according to a twenty-second embodiment of the present invention.

FIG. 28 is a cross-sectional view schematically showing a light-emittingdevice according to a twenty-third embodiment of the present invention.

FIG. 29 is a cross-sectional view schematically showing a light-emittingdevice according to a twenty-fourth embodiment of the present invention.

FIG. 30 is a cross-sectional view schematically showing a light-emittingdevice according to a twenty-fifth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

(A) Among the embodiments illustrated below, a first to a sixthembodiment relate to an edge-emitting type light-emitting device havinga basic structure provided with a light-emitting layer and an opticalwaveguide having a grating.

The first to third embodiments illustrate the case where thelight-emitting layer and a core layer which transmits light are formedas different layers.

(First Embodiment)

FIG. 1A is a schematic oblique view of an edge-emitting typelight-emitting device 11000 (hereinafter referred to as “organiclight-emitting device”) according to the present embodiment. FIG. 1B isa cross-section viewed along the line A—A in FIG. 1A.

In the organic light-emitting device 11000, a first cladding layer 10,core layer 20, anode 30, organic light-emitting layer 40, cathode 50,and second cladding layer 60 are laminated in that order. The refractiveindices of the first cladding layer 10 and the second cladding layer 60in the organic light-emitting device 11000 are designed to be lower thanthe refractive index of each light transmitting layer existing betweenthe first cladding layer 10 and the second cladding layer 60.

The core layer 20 which is the main light transmitting layer is formedalong the organic light-emitting layer 40 through the anode 30. The corelayer 20 comprises a first layer 20 a and a second layer 20 b each ofwhich has a different refractive index. A grating 22 is formed in theboundary area between the first layer 20 a and the second layer 20 b.

The anode 30 is formed from conductive materials which transmit thelight so that the light emitted from the organic light-emitting layer 40is transmitted into the core layer 20. The materials mentioned above canbe used as materials for this transparent electrode. It is preferable todesign the anode 30 and the core layer 20 so that the refractive indicesdiffer from the refractive index of the organic light-emitting layer 40,whereby the light emitted from the organic light-emitting layer 40 isefficiently introduced into the core layer 20.

The grating 22 is preferably a distributed feedback type grating. Such adistributed feedback type grating causes light to resonate inside theoptical waveguide, thereby making it possible to obtain light exhibitingexcellent wavelength selectivity and directivity with a narrow emissionspectrum width. It is preferable that the grating 22 have a λ/4 phaseshifted structure or a gain-coupled structure (not shown). Light with asingle mode can be emitted more easily by the grating 22 having a λ/4phase shifted structure or a gain-coupled structure.

A distributed feedback type grating is also preferable in the followingsecond to fifth embodiments. Therefore, this will not be mentioned inthe description of these embodiments.

In the organic light-emitting device 11000, a first coating layer 100 awith a low reflectance is formed at one edge and a second coating layer110 b with a high reflectance is formed at the other edge. As thesecoating layers, for example, dielectric multi-layered mirrors commonlyused in semiconductor DFB lasers can be used.

It is also preferable that a light-emitting device have such dielectricmulti-layered mirrors in the following second to sixth embodiments.Therefore, this will not be mentioned in the description of theseembodiments.

The action and the effect of the organic, light-emitting device 11000will be described below.

Electrons and holes are injected into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 by applying aprescribed voltage to both the anode 30 and the cathode 50. Excitons areformed in the organic light-emitting layer 40 by recombination of theelectrons and holes. Light such as fluorescent light and phosphorescentlight is emitted when these excitons are deactivated.

The light emitted from the organic light-emitting layer 40 is partiallyreflected by the cathode 50 or the second cladding layer 60. Part of thelight is directly introduced into the core layer 20 through the anode 30which consists of a transparent conductive layer. The light introducedinto the core layer 20 is transmitted inside the core layer 20 towardthe edge thereof by the distributed feedback type transmission becauseof the grating 22, and is emitted from the first low reflectance coatinglayer 100 a.

The light is emitted through distributed feedback in the core layer 20by the grating 22. Because of this, the emitted light has wavelengthselectivity, a narrower emission spectrum width, and excellentdirectivity. Furthermore, light with a single mode can be obtained moreeasily by the grating 22 having a λ/4 phase shifted structure or again-coupled structure. “λ” used herein indicates the wavelength of thelight inside the optical waveguide. The effect of the distributedfeedback type grating is the same as in the following second to fifthembodiments. Therefore, this will not be mentioned in the description ofthese embodiments.

The second cladding layer 60 is formed outside the cathode 50 in theexample shown in the figure. In the case where the cathode 50 can fullyreflect the light emitted from the organic light-emitting layer 40, thesecond cladding layer 60 may be left out. This also applies to otherembodiments having a similar structure.

In the example shown in the figure, the core layer 20 is formed betweenthe first cladding layer 10 and the anode 30. The core layer 20 may beformed between the cathode 50 and the second cladding layer 60. Forexample, in the case where the cathode 50 is thin, the cathode 50 cantransmit light emitted from the light-emitting layer 40. In this case,light with excellent wavelength selectivity and directivity can beemitted from the low reflectance first coating layer 100 a by formingthe core layer 20 having the grating 22 outside the cathode 50 in thesame manner as in the above-described case. This modification alsoapplies to other embodiments having a similar structure.

Either the first layer 20 a or second layer 20 b constituting the corelayer 20 may be a gaseous layer such as air. In the case of forming agrating using such a gaseous layer, the difference in the refractiveindices of the two medium layers constituting the grating can be widerwhile using conventional materials used for light-emitting devices.Therefore, a good grating which is efficient for a desired lightwavelength can be obtained.

As a method for manufacturing the grating or organic light-emittinglayer in the organic light-emitting device 11000 and materialsconstituting each layer, the methods and materials described above canbe appropriately used. For example, in the formation of the grating 22in the core layer 20, a comparatively simple stamping method and thelike can be preferably used. These methods and materials also apply tothe following embodiments.

(Second Embodiment)

FIG. 2 is a cross-sectional view schematically showing an organiclight-emitting device 12000 according to the present embodiment. Thisorganic light-emitting device 12000 forms the grating in the areadifferent from the organic light-emitting device 11000 according to thefirst embodiment.

In the organic light-emitting device 12000, a first cladding layer 10,core layer 20, anode 30, organic light-emitting layer 40, cathode 50,and second cladding layer 60 are laminated in that order. The refractiveindices of the first cladding layer 10 and the second cladding layer 60in the organic light-emitting device 12000 are designed to be lower thanthe refractive index of each light transmitting layer existing betweenthe first cladding layer 10 and the second cladding layer 60.

The light-transmitting core layer 20 is formed along the organiclight-emitting layer 40 through the anode 30. A grating 12 is formed inthe boundary area between the core layer 20 and the first cladding layer10.

The anode 30 is formed from conductive materials which transmit light sothat the light emitted from the organic light-emitting layer 40 isintroduced into the core layer 20. The materials mentioned above can beused as materials for this transparent electrode. The anode 30 and thecore layer 20 are preferably designed so that the refractive indicesdiffer from the refractive index of the organic light-emitting layer 40in order to efficiently introduce the light emitted from the organiclight-emitting layer 40 into the core layer 20.

The action and the effect of the organic light-emitting device 12000will be described below.

Electrons and holes are introduced into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 by applying aprescribed voltage to the anode 30 and the cathode 50. Excitons areformed in the organic light-emitting layer 40 by recombination of theelectrons and holes. Light such as fluorescent light and phosphorescentlight is emitted when these excitons are deactivated. The light emittedfrom the organic light-emitting layer 40 is partially reflected by thecathode 50 or the second cladding layer 60. Part of the light isdirectly introduced into the core layer 20 through the anode 30 whichconsists of a transparent conductive layer.

(Third Embodiment)

FIG. 3 is a cross-sectional view schematically showing an organiclight-emitting device 13000 according to a third embodiment. The organiclight-emitting device 13000 differs from the organic light-emittingdevice 11000 of the first embodiment in having a hole transport layerand an electron transport layer.

In the organic light-emitting device 13000, a first cladding layer 10,anode 30, hole transport layer 70, organic light-emitting layer 40,electron transport layer 80, cathode 50, and second cladding layer 60are laminated in that order. The refractive indices of the firstcladding layer 10 and the second cladding layer 60 in the organiclight-emitting device 13000 are designed to be lower than the refractiveindex of each light transmitting layer existing between the firstcladding layer 10 and the second cladding layer 60.

The feature of this embodiment is that the hole transport layer 70 alsofunctions as the core layer 20 in the first embodiment. Specifically,the hole transport layer 70 which functions as a core layer comprises afirst layer 70 a and a second layer 70 b each having a differentrefractive index. A grating 72 is formed in the boundary area betweenthe first layer 70 a and the second layer 70 b in the direction of lighttransmission.

It is preferable to design the hole transport layer 70 so that theserefractive indices differ from the refractive index of the organiclight-emitting layer 40 in order to efficiently introduce the lightemitted from the organic light-emitting layer 40 into the hole transportlayer 70.

The action and the effect of the organic light-emitting device 13000will be described below.

Electrons are injected from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 throughthe hole transport layer 70 into the organic light-emitting layer 40 byapplying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of the electrons and holes. Light such as fluorescentlight and phosphorescent light is emitted when these excitons aredeactivated. The light emitted from the organic light-emitting layer 40is partially reflected by the cathode 50 or the second cladding layer60. Part of the light is directly introduced into the hole transportlayer 70. The light introduced into the hole transport layer 70 istransmitted inside a waveguide layer 74 toward the edge thereof bydistributed feedback type transmission due to the grating 72. The lightis emitted from a first coating layer with a low reflectance (notshown).

The embodiment illustrates the case of forming the grating 72 in thehole transport layer 70. The grating may be formed in the electrontransport layer 80 instead of the hole transport layer 70. It isunnecessary to form both the hole transport layer and the electrontransport layer. Either of these transport layers may be enough. Thisalso applies to other embodiments.

The grating 72 is formed inside the hole transport layer 70 in thisembodiment. A grating may be formed by the hole transport layer 70 andthe anode 30 made of ITO and the like which is not a metal electrode.

The following fourth and fifth embodiments illustrate the case where thecore layer comprises the organic light-emitting layer.

(Fourth Embodiment)

FIG. 4 is a cross-sectional view schematically showing an organiclight-emitting device 14000 according to the present embodiment.

A feature of this organic light-emitting device 14000 is that an organiclight-emitting layer 40 is sandwiched between a hole transport layer 70and a electron transport layer 80 and a grating is formed in the organiclight-emitting layer 40.

In the organic light-emitting device 14000, a first cladding layer 10,anode 30, hole transport layer 70, organic light-emitting layer 40,electron transport layer 80, cathode 50, and second cladding layer 60are laminated in that order. The refractive indices of the firstcladding layer 10 and the second cladding layer 60 in the organiclight-emitting device 14000 are designed to be lower than the refractiveindex of each light transmitting layer existing between the firstcladding layer 10 and the second cladding layer 60.

In this embodiment, the organic light-emitting layer 40 and the electrontransport layer 80 also function as a light-transmitting core layer. Agrating 42 is formed in the boundary area between the organiclight-emitting layer 40 and the electron transport layer 80. Therefore,the refractive indices of the organic light-emitting layer 40 and theelectron transport layer 80 are designed to be different.

The action and the effect of the organic light-emitting device 14000will be described below.

Electrons are injected from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 throughthe hole transport layer 70 into the organic light-emitting layer 40 byapplying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of the electrons and holes. Light such as fluorescentlight and phosphorescent light is emitted when these excitons aredeactivated. The light emitted from the organic light-emitting layer 40is transmitted inside the organic light-emitting layer 40 and theelectron transport layer 80 toward the edges thereof by distributedfeedback type transmission due to the grating 42. The light is emittedfrom a first coating layer with a low reflectance (not shown).

According to this organic light-emitting device 14000, because the lightemitted from the organic light-emitting layer 40 is transmitted insidethe organic light-emitting layer 40, efficient light emission is ensuredby appropriately selecting the materials for the organic light-emittinglayer 40.

The grating 42 is formed by the organic light-emitting layer 40 and theelectron transport layer 80 in the organic light-emitting device 14000of this embodiment. In the case of using a nonmetallic substance such asdiamond as the material for the cathode 50, the grating may be formed bythe cathode 50 and the electron transport layer 80. If the electrontransport layer 80 is not formed, the grating may be formed by thecathode 50 and the organic light-emitting layer 40.

(Fifth Embodiment)

FIG. 5 is a cross-sectional view schematically showing an organiclight-emitting device 15000 according to the present embodiment. In thisorganic light-emitting device 15000, the organic light-emitting layerconstitutes the grating as in the fourth embodiment. However, thisorganic light-emitting device does not have a second cladding layer.

In the organic light-emitting device 15000, a cladding layer 10, anode30, hole transport layer 70, organic light-emitting layer 40, andcathode 50 are laminated in that order. A grating 72 is formed in theboundary area between the organic light-emitting layer 40 and the holetransport layer 70. Therefore, the refractive indices of the organiclight-emitting layer 40 and the hole transport layer 70 are designed tobe different.

In this organic light-emitting device 15000, the organic light-emittinglayer 40 and hole transport layer 70 function as a core layer whichtransmits light.

The action and the effect of the organic light-emitting device 15000will be described below.

Electrons and holes are introduced into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 through the holetransport layer 70 by applying a prescribed voltage to the anode 30 andthe cathode 50. Excitons are formed in the organic light-emitting layer40 by recombination of the electrons and holes. Light such asfluorescent light and phosphorescent light is emitted when theseexcitons are deactivated. The light emitted from the organiclight-emitting layer 40 is transmitted inside the organic light-emittinglayer 40 and the hole transport layer 70 toward the edges thereof bydistributed feedback type transmission due to the grating 72. The lightis emitted from a first coating layer with a low reflectance (notshown).

According to this organic light-emitting device 15000, because part ofthe organic light-emitting layer 40 constitutes the grating 72, light isemitted with high efficiency by appropriately selecting the materialsfor the organic light-emitting layer 40.

(Sixth Embodiment)

FIG. 6 is a cross-sectional view schematically showing an organiclight-emitting device 16000 according to the present embodiment. Thisorganic light-emitting device 16000 differs from the above-describedorganic light-emitting devices in having a distributed Braggreflection-type grating.

In the organic light-emitting device 16000, a cladding layer 10, anode30, hole transport layer 70, organic light-emitting layer 40, andcathode 50 are laminated in that order. The refractive index of thecladding layer 10 in the organic light-emitting device 16000 is designedto be lower than the refractive index of each light-transmitting layer.

A grating 72 formed in the boundary area between the hole transportlayer 70 and an air layer 90 constitutes a distributed Bragg-typegrating having an air gap. A concavity 42 is formed in part of thesurface of the hole transport layer 70. The organic light-emitting layer40 is formed in the concavity 42. The cathode 50 is formed on theorganic light-emitting layer 40. In the organic light-emitting device16000, the hole transport layer 70 and the air layer 90 function as alight-transmitting core layer.

The distributed Bragg-type grating 72 causes light to resonate, wherebylight with excellent wavelength selectivity and directivity can beobtained.

The action and the effect of the organic light-emitting device 16000will be described below.

Electrons and holes are introduced into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 through the holetransport layer 70 by applying a prescribed voltage to the anode 30 andthe cathode 50. Excitons are formed in the organic light-emitting layer40 by recombination of the electrons and holes. Light such asfluorescent light and phosphorescent light is emitted when theseexcitons are deactivated.

Because this embodiment has the distributed Bragg reflection-typegrating 72, light emitted from the organic light-emitting layer 40 isreflected by the grating at both sides of the organic light-emittinglayer 40 and resonates. Therefore, the light emitted from the organiclight-emitting layer 40 resonates more efficiently and is transmittedinside the hole transport layer 70 and the air layer 90 toward the edgesthereof. The light is emitted from a first coating layer with a lowreflectance (not shown). Because the light is emitted after resonatingby the distributed Bragg reflection-type grating 72, the light not onlyhas excellent wavelength selectivity and directivity but also is emittedwith high efficiency.

The grating 72 is formed in the hole transport layer 70 in the exampleshown in the figure. The grating may be formed in an electron transportlayer which is formed instead of the hole transport layer. A core layermay be formed from materials with small light absorption instead offorming the hole transport layer or electron transport layer. One oflayers constituting gratings, which comprise air in the example shown inthe figure, may be a layer formed from other materials. Furthermore, atleast either the hole transport layer or the electron transport layermay be embedded into the concavity 42 in addition to the organiclight-emitting layer 40.

The grating is formed by the hole transport layer 70 on the anode 30 andthe air layer 90 in the organic light-emitting device 16000 shown inFIG. 6. For example, a distributed Bragg reflection-type grating 22shown in FIG. 7 may be formed using two medium layers each of which hasa different refractive index (a core layer 20 and an air layer 90 inFIG. 7) below the anode 30.

(B) The following seventh to tenth embodiments illustrate examples inwhich a light-emitting layer constitutes a medium layer of a grating andthe light-emitting layer is discontinuous.

(Seventh Embodiment)

FIG. 8 is a cross-sectional view schematically showing an edge-emittingtype organic light-emitting device 21000 according to the presentembodiment.

In the organic light-emitting device 21000, a first cladding layer 10,anode 30, hole transport layer 70, organic light-emitting layer 40,cathode 50, and second cladding layer 60 are laminated in that order.The refractive indices of the first cladding layer 10 and the secondcladding layer 60 in the organic light-emitting device 21000 aredesigned to be lower than the refractive index of each lighttransmitting layer existing between the first cladding layer 10 and thesecond cladding layer 60. The organic light-emitting layer 40 issandwiched between the hole transport layer 70 and the cathode 50.

In this embodiment, at least the organic light-emitting layer 40 and thehole transport layer 70 also function as a light-transmitting corelayer. A grating 110 is formed by the organic light-emitting layer 40and the hole transport layer 70. Therefore, the refractive indices ofthe organic light-emitting layer 40 and the hole transport layer 70 aredesigned to be different. Specifically, the grating 110 is formed byforming concavities 72 with a prescribed pitch and depth in the upperportion of the hole transport layer 70 and filling the organiclight-emitting layer 40 therein. Therefore, the organic light-emittinglayers 40 are separated at a prescribed pitch.

The grating 110 is preferably a distributed feedback type grating. Lighthaving excellent wavelength selectivity, a narrow emission spectrumwidth, and superior directivity can be obtained by forming such adistributed feedback type grating. It is preferable that the grating 110have a λ/4 phase shifted structure or a gain-coupled structure (notshown). Such a λ/4 phase shifted structure or a gain-coupled structureensures that the light is emitted with a single mode.

A distributed feedback type grating is also preferable in the followingeighth to tenth embodiments. Therefore, this will not be furthermentioned in the description of these embodiments.

In the organic light-emitting device 21000, a first coating layer with alow reflectance is formed at one edge and a second coating layer with ahigh reflectance is formed at the other edge (not shown). As thesecoating layers, for example, dielectric multi-layered mirrors commonlyused in semiconductor DFB lasers can be used.

It is also preferable that a light-emitting device have such dielectricmulti-layered mirrors in the following eighth to tenth embodiments.Therefore, this will not be further mentioned in the description ofthese embodiments.

Although not shown in the figure showing the organic light-emittingdevice 21000, it is preferable to form an insulating layer on thesurface of the convexities of the hole transport layer 70, in otherwords, between the hole transport layer 70 and the cathode 50 in thearea where the light-emitting layers 40 are not formed. The currentinjection efficiency into the light-emitting layer 40 can be improved byforming such an insulating layer.

The action and the effect of the organic light-emitting device 21000will be described below.

Electrons and holes are introduced into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 through the holetransport layer 70 by applying a prescribed voltage to the anode 30 andthe cathode 50. Excitons are formed in the organic light-emitting layer40 by recombination of the electrons and holes. Light such asfluorescent light and phosphorescent light is emitted when theseexcitons are deactivated. The light emitted from the organiclight-emitting layer 40 is transmitted inside a core layer toward theedge thereof by distributed feedback type transmission due to thegrating 110. The light is emitted from the first coating layer with alow reflectance.

The light is emitted through distributed feedback by the grating 110.Because of this, the emitted light has wavelength selectivity, anarrower emission spectrum width, and excellent directivity.Furthermore, light with a single mode can be obtained more easily by thegrating 110 having a λ/4 phase shifted structure or a gain-coupledstructure. “λ” used herein indicates the wavelength of the light insidethe optical waveguide. This also applies to the following eighth totenth embodiments and will not be mentioned in the description of theseembodiments.

According to this organic light-emitting device 21000, because the lightemitted from the organic light-emitting layer 40 is transmitted insidethe organic light-emitting layer 40, efficient light emission is ensuredby appropriately selecting the materials for the organic light-emittinglayer 40.

(Eighth Embodiment)

FIG. 9 is a cross-sectional view schematically showing an edge-emittingtype organic light-emitting device 22000 according to the presentembodiment.

In the organic light-emitting device 22000, a first cladding layer 10,anode 30, hole transport layer 70, organic light-emitting layer 40,electron transport layer 80, cathode 50, and second cladding layer 60are laminated in that order. The refractive indices of the firstcladding layer 10 and the second cladding layer 60 in the organiclight-emitting device 22000 are designed to be lower than the refractiveindex of each light transmitting layer existing between the firstcladding layer 10 and the second cladding layer 60. The organiclight-emitting layer 40 is sandwiched between the hole transport layer70 and the cathode 50.

In this embodiment, at least the organic light-emitting layer 40 and theelectron transport layer 80 also function as a light-transmitting corelayer. A grating 110 is formed by the organic light-emitting layer 40and the electron transport layer 80. Therefore, the refractive indicesof the organic light-emitting layer 40 and the electron transport layer80 are designed to be different. Specifically, the grating 110 is formedby forming the organic light-emitting layers 40 with a prescribed pitchand height on the hole transport layer 70 and filling part of theelectron transport layer 80 into the concavities formed between theadjacent organic light-emitting layers 40.

Although not shown in the figure illustrating the organic light-emittingdevice 22000, it is preferable to form an insulating layer between thehole transport layer 70 and the electron transport layer 80 in the areawhere the light-emitting layers 40 are not formed. The efficiency ofcurrent injection into the light-emitting layer 40 can be improved byforming such an insulating layer.

The action and the effect of the organic light-emitting device 22000will be described below.

Electrons are injected from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 throughthe hole transport layer 70 into the organic light-emitting layer 40 byapplying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of the electrons and holes. Light such as fluorescentlight and phosphorescent light is emitted when these excitons aredeactivated. The light emitted from the organic light-emitting layer 40is transmitted inside a core layer toward the edge thereof bydistributed feedback type transmission due to the grating 110. The lightis emitted from the first coating layer with a low reflectance (notshown).

According to this organic light-emitting device 22000, because the lightemitted from the organic light-emitting layer 40 is transmitted insidethe organic light-emitting layer 40, efficient light emission is ensuredby appropriately selecting the materials for the organic light-emittinglayer 40.

(Ninth Embodiment)

FIG. 10 is a cross-sectional view schematically showing an edge-emittingtype organic light-emitting device 23000 according to the presentembodiment.

In the organic light-emitting device 23000, a first cladding layer 10,anode 30, organic light-emitting layer 40, electron transport layer 80,cathode 50, and second cladding layer 60 are laminated in that order.The refractive indices of the first cladding layer 10 and the secondcladding layer 60 in the organic light-emitting device 23000 aredesigned to be lower than the refractive index of each lighttransmitting layer existing between the first cladding layer 10 and thesecond cladding layer 60. The organic light-emitting layer 40 isinterposed between the anode 30 and the electron transport layer 80. Theorganic light-emitting layer 40 constitutes the grating 110.

In this embodiment, at least the anode 30, organic light-emitting layer40, and electron transport layer 80 also function as alight-transmitting core layer. The grating 110 is formed by the organiclight-emitting layer 40 and anode 30. Therefore, the refractive indicesof the organic light-emitting layer 40 and the electron transport layer80 are designed to be different and a transparent conductive layerconstitutes the anode 30. Specifically, the grating 110 is formed byforming concavities 32 with a prescribed pitch and depth in the upperportion of the anode 30 and filling the organic light-emitting layer 40therein. Therefore, the organic light-emitting layers 40 are separate ata prescribed pitch.

The action and the effect of the organic light-emitting device 23000will be described below.

Electrons are injected from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 into theorganic light-emitting layer 40 by applying a prescribed voltage to theanode 30 and the cathode 50. Excitons are formed in the organiclight-emitting layer 40 by recombination of the electrons and holes.Light such as fluorescent light and phosphorescent light is emitted whenthese excitons are deactivated. The light emitted from the organiclight-emitting layer 40 is transmitted inside a core layer toward theedge thereof by distributed feedback type transmission due to thegrating 110. The light is emitted from the first coating layer with alow reflectance (not shown).

According to this organic light-emitting device 23000, because the lightemitted from the organic light-emitting layer 40 is transmitted insidethe organic light-emitting layer 40, efficient light emission is ensuredby appropriately selecting the materials for the organic light-emittinglayer 40.

(Tenth Embodiment)

FIG. 11 is a cross-sectional view schematically showing an edge-emittingtype organic light-emitting device 24000 according to the presentembodiment.

In the organic light-emitting device 24000, a first cladding layer 10,anode 30, hole transport layer 70, The grating 110 formed by an organiclight-emitting layer 40 and medium layer 90, cathode 50, and secondcladding layer 60 are laminated in that order. The refractive indices ofthe first cladding layer 10 and the second cladding layer 60 in theorganic light-emitting device 24000 are designed to be lower than therefractive index of each light transmitting layer existing between thefirst cladding layer 10 and the second cladding layer 60. The organiclight-emitting layer 40 is interposed between the hole transport layer70 and the cathode 50.

In this embodiment, at least the grating 110 comprising the organiclight-emitting layer 40 and the electron transport layer 80 alsofunction as a light-transmitting core layer. A grating 110 is formed bythe organic light-emitting layer 40 and the medium layer 90. Therefore,the refractive indices of the organic light-emitting layer 40 and themedium layer 90 are designed to be different. Specifically, the grating110 is formed by forming the medium layer 90 with a prescribed pitch andheight on the hole transport layer 70 and filling the organiclight-emitting layers 40 between the medium layers 90. Therefore, theorganic light-emitting layers 40 are separated at a prescribed pitch.The organic light-emitting layers 40 may be formed prior to the mediumlayers 90. The medium layers 90 are preferably formed from organic orinorganic insulation materials. The current injection efficiency intothe light-emitting layer 40 can be improved if the medium layers 90 haveinsulating properties.

The action and the effect of the organic light-emitting device 24000will be described below.

Electrons and holes are introduced into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 through the holetransport layer 70 by applying a prescribed voltage to the anode 30 andthe cathode 50. Excitons are formed in the organic light-emitting layer40 by recombination of the electrons and holes. Light such asfluorescent light and phosphorescent light is emitted when theseexcitons are deactivated. The light emitted from the organiclight-emitting layer 40 is transmitted inside a core layer toward theedge thereof by distributed feedback type transmission due to thegrating 110. The light is emitted from the first coating layer with alow reflectance (not shown).

According to this organic light-emitting-device 24000, because the lightemitted from the organic light-emitting layer 40 is transmitted insidethe organic light-emitting layer 40, efficient light emission is ensuredby appropriately selecting the materials for the organic light-emittinglayer 40.

The above seventh to tenth embodiments illustrate examples using theorganic light-emitting layer as a medium for a grating. The presentinvention is not limited to these embodiments and various embodimentscan be employed. For example, a grating may consist of an organiclight-emitting layer and other layers and such other layers may be agaseous layer such as air other than the layers described for the aboveembodiments. In the case of forming a grating with an air gap structureusing such a gaseous layer, the difference in the refractive indices ofthe two medium layers which constitute the grating can be wider usingcommon materials employed for the light-emitting device, therefore, agood grating which is efficient for a desired light wavelength.

(C) The following eleventh to fourteenth embodiments illustrate examplesof an optical fiber integrated light-emitting device comprising anorganic light-emitting layer, optical waveguide having a grating, andoptical fiber section. In these embodiments, a section having alight-emitting function equivalent to the light-emitting devicedescribed above is referred to as an “EL element section”.

(Eleventh Embodiment)

FIG. 12 is a schematic vertical section of an organic light-emittingdevice 31000 according to the present embodiment. FIG. 13 is a schematiccross-section viewed along the line B—B in FIG. 12.

The light-emitting device 31000 comprises an optical fiber section 200and an EL element section 100 formed at the end of the optical fibersection 200.

The optical fiber section 200 comprises a core layer 90 and a claddinglayer 95 surrounding the core layer 90.

Each layer in the EL element section 100 is formed in almost concentriccircles as shown in cross-section in FIG. 13. An EL core layer 20, anode30, organic light-emitting layer 40, cathode 50, and EL cladding layer60 are laminated in that order from the center. The refractive index ofthe EL cladding layer 60 in the light-emitting device 31000 is designedto be lower than the refractive index of each light transmitting layerencircled by the EL cladding layer 60.

The light-transmitting EL core layer 20 formed along the inside of theanode 30 is a core-layer-continuing portion 92 which continues from thecore layer 90 of the optical fiber section 200. In the EL core layer 20,a first layer 20 a and a second layer 20 b each of which has a differentrefractive index continue alternately in the direction of the length toform a grating 22. The light-emitting device 31000 comprises the EL corelayer 20 which comprises the core-layer-continuing portion 92 whichcontinues from the core layer 90 of the optical fiber section 200,whereby the light output from the EL core layer 20 is transmitted to theoptical fiber with high efficiency. Moreover, this highly efficientcombination is obtained without performing a delicate opticaladjustment.

The anode 30 is formed from conductive materials which transmit light sothat the light emitted from the organic light-emitting layer 40 isintroduced into the EL core layer 20. The materials mentioned above canbe used as materials for this transparent electrode. It is preferable todesign the anode 30 and the EL core layer 20 so that the refractiveindices differ from the refractive index of the organic light-emittinglayer 40, whereby the light emitted from the organic light-emittinglayer 40 is efficiently introduced into the EL core layer 20. Inparticular, the refractive index of the EL core layer 20 is preferablydesigned to be higher than the refractive index of the organiclight-emitting layer 40.

The grating 22 is preferably a distributed feedback type grating. Such adistributed feedback type grating causes light to resonate, therebymaking it possible to obtain excellent light exhibiting wavelengthselectivity and directivity with a narrow emission spectrum width. It ispreferable that the grating 22 have a λ/4 phase shifted structure or again-coupled structure (not shown). Such a λ/4 phase shifted structureor a gain-coupled structure ensures that the light is emitted with asingle mode.

It is also preferable to form a distributed feedback type grating as inthe following twelfth to fourteenth embodiments. Therefore, this willnot be further mentioned in the description of these embodiments.

In the light-emitting device 31000, a coating layer 14 with a highreflectance is formed at one end. As the coating layer 14, for example,dielectric multi-layered mirrors commonly used in semiconductor DFBlasers can be used.

It is also preferable to provide such a dielectric multi-layered mirroras in the following twelfth to fourteenth embodiments. Therefore, thiswill not be further mentioned in the description of these embodiments.

The action and the effect of the light-emitting device 31000 will bedescribed below.

Electrons and holes are introduced into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 by applying aprescribed voltage to the anode 30 and the cathode 50. Excitons areformed in the organic light-emitting layer 40 by recombination of theelectrons and holes. Light such as fluorescent light and phosphorescentlight is emitted when these excitons are deactivated.

The light emitted from the organic light-emitting layer 40 is partiallyreflected by the cathode 50 or the EL cladding layer 60. Part of thelight is directly introduced into the EL core layer 20 through the anode30 made of a transparent conductive layer. The light introduced into theEL core layer 20 is transmitted inside the EL core layer 20 bydistributed feedback type transmission due to the grating 22 and isemitted to the core layer 90 of the optical fiber section 200. The lightis emitted through distributed feedback in the EL core layer 20 by thegrating 22. Because of this, the emitted light has wavelengthselectivity, a narrower emission spectrum width, and excellentdirectivity.

Furthermore, light with a single mode can be obtained more easily by thegrating 22 having a λ/4 phase shifted structure or a gain-coupledstructure. “λ” used herein indicates the wavelength of the light insidethe optical waveguide. This also applies to the following twelfth tofourteenth embodiments and will not be further mentioned in thedescription of these embodiments.

Because the EL core layer 20 comprises the core-layer-continuing portion92 which continues from the core layer 90 of the optical fiber section200, the light output from the EL core layer 20 is introduced into theoptical fiber section 200 with high efficiency. Moreover, there is noneed to perform a delicate optical adjustment.

The EL cladding layer 60 is formed outside the cathode 50 in the exampleshown in the figure. In the case where the cathode 50 can fully reflectthe light emitted from the organic light-emitting layer 40, the ELcladding layer 60 may be omitted. This also applies to the followingtwelfth to fourteenth embodiments.

The anode 30 is formed so as to be in contact with the EL core layer 20in the example shown in the figure. The cathode 50 may be formed so asto be in contact with the EL core layer and the anode 30 may be formedoutside the organic light-emitting layer 40. For example, in the casewhere the cathode 50 is thin, light emitted from the light-emittinglayer 40 can penetrate the cathode 50. In this case, light withexcellent wavelength selectivity and directivity can be emitted to thecore layer 90 of the optical fiber section 200 in the same manner as inthe above cases by forming the EL core layer 20 having the grating 22inside the cathode 50. This modification also applies to the followingtwelfth to fourteenth embodiments.

Instead of forming the anode 30 and cathode 50 to be in contact with theorganic light-emitting layer 40, a hole transport layer may be formedbetween the anode 30 and the organic light-emitting layer 40 or anelectron transport layer may be formed between the cathode 50 and theorganic light-emitting layer 40.

In order to obtain a good external connection, it is preferable toexpose the peripheries, that is, the curved surfaces of the anode 30 andthe cathode 50 to secure an electrical connection in the wide area.

As a method of manufacturing a grating 22 or organic light-emittinglayer 40 of the light-emitting device 31000 and materials constitutingeach layer, the methods and materials described above can beappropriately used. For example, in the formation of the grating 22 inthe EL core layer 20, a method of forming a refractive indexdistribution by irradiation and the like can be preferably used. Thesemethods and materials also apply to the following twelfth to fourteenthembodiments.

(Twelfth Embodiment)

FIG. 14 is a schematic vertical section of a light-emitting device 32000according to the present embodiment. FIG. 15 is a schematiccross-section viewed along the line D—D in FIG. 14.

In the light-emitting device 32000, the EL element section is not formedin concentric circles like the eleventh embodiment as shown in thesefigures. The feature of the light-emitting device 32000 is as follows.In the light-emitting device 32000 according to this embodiment, almosthalf of a core-layer-continuing portion 92 and acladding-layer-continuing portion 97 which continue respectively from acore layer 90 and a cladding layer 95 of an optical fiber section 200 isremoved horizontally. An anode 30, organic light-emitting layer 40,cathode 50, and EL cladding layer 60 are laminated almost flat on thesection. Other features are as same as in the eleventh embodiment anddescription thereof is omitted. Corresponding sections in each figureare indicated by the same symbols as in the eleventh embodiment.

As shown in cross-sectional FIG. 15, almost half of thecore-layer-continuing portion 92 and the cladding-layer-continuingportion 97 which continue respectively from the core layer 90 and thecladding layer 95 of the optical fiber section 200 is removedhorizontally in the EL element section 300. The anode 30, organiclight-emitting layer 40, cathode 50, and EL cladding layer 60 arelaminated almost flat on the section. The anode 30 is formed flat to becontinuously in contact with the core-layer-continuing portion 92. Theorganic light-emitting layer 40 is formed flat to be in contact with theother side of the anode 30. The cathode 50 is formed flat to be incontact with the organic light-emitting layer 40. The EL cladding layer60 is formed to enclose the anode 30, organic light-emitting layer 40,and cathode 50 in the directions of the lengths. The EL cladding layer60 is joined with the cladding-layer-continuing portion 97. Therefractive index of the EL cladding layer 60 in the light-emittingdevice 32000 is designed to be lower than the refractive index of eachlight transmitting layer enclosed by the EL cladding layer 60.

The EL core layer 20 is formed along the bottom of the anode 30 andcomprises the core-layer-continuing portion 92 which continues from thecore layer 90 of the optical fiber section 200. In the EL core layer 20,a first layer 20 a and a second layer 20 b, each of which has adifferent refractive index, continue alternately in the direction of thelength to form a grating 22. The light-emitting device 32000 comprisesthe EL core layer 20 which comprises the core-layer-continuing portion92 which continues from the core layer 90 of the optical fiber section200, whereby the light output from the EL core layer 20 is transmittedto the optical fiber with high efficiency. Moreover, this highlyefficient combination is obtained without performing a delicate opticaladjustment.

Either the first layer 20 a or second layer 20 b which constitutes theEL core layer 20 may be a gaseous layer such as air. In the case offorming the grating 22 by such a gaseous layer, the grating 22 having alarge difference in the refractive index between the layers 20 a and 20b can be easily formed.

In the EL element section 300 according to this embodiment, the anode30, organic light-emitting layer 40, and cathode 50 are formedcorresponding to the width of the EL core layer 20 as shown in FIG. 15.For example, the anode 30, organic light-emitting layer 40, and cathode50 may all be formed over the EL core layer 20 and thecladding-layer-continuing portion 97 on the section shown in FIG. 15.

(Thirteenth Embodiment)

FIG. 16 is a schematic vertical section of a light-emitting device 33000according to the present embodiment. FIG. 17 is a schematiccross-section viewed along the line F—F in FIG. 16.

This light-emitting device 33000 differs from the light-emitting device31000 according to the eleventh embodiment in that the EL core layer 20comprises the core-layer-continuing portion 92 and the anode 30. Otherfeatures are as same as in the eleventh embodiment and descriptionthereof is omitted. Corresponding sections in each figure are indicatedby the same symbols as in the eleventh embodiment.

The light-transmitting EL core layer 20 is formed by the anode 30 andthe core-layer-continuing portion 92. In the EL core layer 20, a grating32 is formed in the boundary area between the anode 30 and thecore-layer-continuing portion 92 where the first layer 20 a (anode 30)and the second layer 20 b (core-layer-continuing portion 92) continuealternately in the direction of the length. The light-emitting device33000 comprises the EL core layer 20 which comprises thecore-layer-continuing portion 92 which continues from the core layer 90of the optical fiber section 200, whereby the light output from the ELcore layer 20 is transmitted to the optical fiber with high efficiency.Moreover, this highly efficient combination is obtained withoutperforming a delicate optical adjustment.

It is preferable to design the anode 30 and the core-layer-continuingportion 92 so that the refractive indices differ from the refractiveindex of the organic light-emitting layer 40, whereby the light emittedfrom the organic light-emitting layer 40 is efficiently introduced intothe anode 30 and the core-layer-continuing portion 92.

The action and the effect of the light-emitting device 33000 will bedescribed below.

Electrons are introduced from the cathode 50 and holes are injected fromthe anode 30 into the organic light-emitting layer 40 by applying aprescribed voltage to the anode 30 and the cathode 50. Excitons areformed in the organic light-emitting layer 40 by recombination of theelectrons and holes. Light such as fluorescent light and phosphorescentlight is emitted when these excitons are deactivated. The light emittedfrom the organic light-emitting layer 40 is partially reflected by thecathode 50 or the EL cladding layer 60. Part of the light is directlyintroduced into the anode 30 and the core-layer-continuing portion 92.The light introduced into the anode 30 and the core-layer-continuingportion 92 is transmitted inside the EL core layer 20 toward the edgethereof by distributed feedback type transmission due to the grating 32and is emitted to the core layer 90 of the optical fiber section 200.

The embodiment illustrates the case of forming the grating 32 by theanode 30 and the core-layer-continuing portion 92. The grating 32 may beformed by the cathode 50 and the core-layer-continuing portion 92instead of the anode 30 and the core-layer-continuing portion 92 byexchanging the positions of the anode 30 and the cathode 50.

In the same manner as in the differences between the eleventh embodimentand the twelfth embodiment, almost half of the core-layer-continuingportion 92 and the cladding-layer-continuing portion 97 which continuerespectively from a core layer 90 and a cladding layer 95 of an opticalfiber section 200 may be removed horizontally, instead of forming the ELelement section 400 in concentric circles. The anode 30, organiclight-emitting layer 40, cathode 50, and EL cladding layer 60 may belaminated almost flat on the section.

(Fourteenth Embodiment)

FIG. 18 is a schematic vertical section of a light-emitting device 34000according to the present embodiment. FIG. 19 is a schematiccross-section viewed along the line H—H in FIG. 18.

This light-emitting device 34000 differs from the light-emitting device31000 according to the eleventh embodiment in that the EL core layer 20comprises the anode 30 and medium layers 46 formed in the anode 30 atintervals in the direction of the length. Other features are the same asin the eleventh embodiment and further description thereof is omitted.Corresponding sections in each figure are indicated by the same symbolsas in the eleventh embodiment.

In the light-emitting device 34000, the light-transmitting EL core layer20 comprises the anode 30 and the medium layers 46 formed in the anode30. In the EL core layer 20, the first layer 20 a (part of the anode 30)and the second layer 20 b (medium layers 46) having different refractiveindices continue alternately to form a grating 42.

The above-mentioned materials for the optical waveguide can be used asthe material for the medium layers 46.

As shown in FIGS. 18 and 19, the light-emitting device 34000 comprisesthe EL core layer 20 which is formed so as to encircle thecore-layer-continuing portion 92 which continues from the core layer 90of the optical fiber section 200, whereby the light output from the ELcore layer 20 is transmitted to the optical fiber with high efficiency.Moreover, this highly efficient combination is obtained withoutperforming a delicate optical adjustment.

It is preferable to design the refractive indices of anode 30, mediumlayers 46, and the core-layer-continuing portion 92 to be different fromthe refractive index of the organic light-emitting layer 40 so that thelight emitted from the organic light-emitting layer 40 is efficientlyintroduced into the anode 30, medium layers 46, andcore-layer-continuing portion 92.

The action and the effect of the light-emitting device 34000 will bedescribed below.

Electrons are introduced from the cathode 50 and holes are injected fromthe anode 30 into the organic light-emitting layer 40 by applying aprescribed voltage to the anode 30 and the cathode 50. Excitons areformed in the organic light-emitting layer 40 by recombination of theelectrons and holes. Light such as fluorescent light and phosphorescentlight is emitted when these excitons are deactivated. The light emittedfrom the organic light-emitting layer 40 is partially reflected by thecathode 50 or the EL cladding layer 60. Part of the light is directlyintroduced into the anode 30 and the medium layers 46. The lightintroduced into the anode 30 and the medium layers 46 is transmittedinside the EL core layer 20 toward the edge thereof by the distributedfeedback type transmission due to the grating 42 and is emitted to thecore layer 90 of the optical fiber section 200.

This embodiment illustrates the case of forming the grating 42 by theanode 30 and the medium layers 46 formed at intervals. The grating 42may be formed by the cathode 50 and the medium layers 46 by exchangingthe positions of the anode 30 and the cathode 50.

In the same manner as in the difference between the eleventh embodimentand the twelfth embodiment, almost half of the core-layer-continuingportion 92 and the cladding-layer-continuing portion 97 which continuerespectively from a core layer 90 and a cladding layer 95 of an opticalfiber section 200 may be removed horizontally, instead of forming the ELelement section 500 in concentric circles. The anode 30, medium layers46, organic light-emitting layer 40, cathode 50, and EL cladding layer60 may be laminated almost flat on the section.

According to the above eleventh to fourteenth embodiments, alight-emitting device with a narrow wavelength spectral width, excellentdirectivity, and superior positioning precision between thelight-emission part and transmission part is provided.

(D) The following fifteenth to twenty-fifth embodiments illustrate alight-emitting device comprising an organic light-emitting layer and anoptical waveguide having a grating which constitutes a photonic bandgap.

Among the embodiments described below, the fifteenth to seventeenthembodiments illustrate the case where an organic light-emitting layer isformed in a defect of a grating.

(Fifteenth Embodiment)

FIG. 20 is a cross-sectional view schematically showing a light-emittingdevice 41000 according to the present embodiment. The light-emittingdevice 41000 comprises a substrate 10, anode 30, hole transport layer70, organic light-emitting layer 40, cathode 50, and grating 110.

The grating 110 comprises a defect 120 and first and second gratings 110a and 110 b at each side of the defect 120. These gratings 110 a and 110b can form a photonic band gap to a prescribed wavelength range on thebasis of the shape (dimensions) and combinations of the media. Firstmedium layers 130 and second medium layers 140 having differentrefractive indices are arranged alternately in the gratings 110 a and110 b. The second medium layer 140 is formed of a hole transport layer70. The materials for the first medium layers 130 are not limitedinsofar as the first medium layers 130 can form a photonic band gap byperiodic distribution with the second medium layers 140. For example,the second medium layer may be a gaseous body such as air. In the caseof forming a grating with a so-called air-gap structure by such agaseous layer, the difference in the refractive indices of the twomedium layers which constitute a grating can be increased while usingmaterials commonly used for light-emitting devices.

The organic light-emitting layer 40 is embedded into the defect 120. Inthe present embodiment, the defect 120 of the grating 110 also functionsas the light-emitting layer 40. The defect 120 is formed so that theenergy level caused by the vacancy exists inside the emission spectrumof the organic light-emitting layer 40 by the electrically pumping.

The cathode 50 is formed locally to cover the surface of the organiclight-emitting layer 40. An electric current is intensively supplied tothe organic light-emitting layer 40 by forming the cathode 50 on onlythe organic light-emitting layer 40, whereby the electric current losscan be reduced.

Because the light is confined by the grating 110 having aone-dimensional photonic band gap in the light-emitting device 41000according to this embodiment, optical transmission is controlled only inthe direction in which the grating 110 extends (direction X in FIG. 1).Therefore, light with a leakage mode is transmitted in other directions.In order to control the transmission of the light with such a leakagemode, a cladding layer or a dielectric multiple-layered mirror may beoptionally formed to confine the light. This also applies to thefollowing sixteenth to twenty-fifth embodiments and will not be furthermentioned in the description of these embodiments.

The action and the effect of the light-emitting device 41000 will bedescribed below.

Electrons and holes are introduced into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 through the holetransport layer 70 by applying a prescribed voltage to the anode 30 andthe cathode 50. Excitons are formed in the organic light-emitting layer40 by recombination of these electrons and holes. Light with awavelength range equivalent to the photonic band gap of the grating 110cannot be transmitted inside the grating 110. The excitons are returnedto the ground state at an energy level caused by the vacancy and onlythe light with a wavelength range equivalent to this energy level isemitted. Therefore, light with a remarkably narrow emission spectrumwidth prescribed by the width of the energy level caused by the vacancycan be obtained with high efficiency.

The function of the photonic band gap also applies to the followingsixteenth to twenty-fifth embodiments. Therefore, this will not befurther mentioned in the description of these embodiments.

As a method of manufacturing the grating 110 of the light-emittingdevice 41000 and materials constituting each layer, the methods andmaterials described above can be appropriately used. These methods andmaterials also apply to the following other embodiments.

(Sixteenth Embodiment)

FIG. 21 is a cross-sectional view schematically showing a light-emittingdevice 42000 according to the present embodiment. The light-emittingdevice 42000 comprises a substrate 10, anode 30, hole transport layer70, organic light-emitting layer 40, electron transport layer 80,cathode 50, and grating 110. The anode 30 and the cathode 50 are formedcontinuously. The hole transport layer 70 and the electron transportlayer 80 are formed discontinuously.

The grating 110 comprises a defect 120, and the organic light-emittinglayer 40 is formed in this defect 120. First and second gratings 110 aand 110 b are formed at both sides of the defect 120. These gratings 110a and 110 b can form a photonic band gap to a prescribed wavelengthrange. The first medium layers 130 and the second medium layer 140having different refractive indices are arranged alternately in thegratings 110 a and 110 b. The first medium layers 130 are formed fromthe anode 30 to the cathode 50. The second medium layers 140 standbetween the hole transport layer 70 and the electron transport layer 80.Both the first and second medium layers 130 and 140 have insulatingproperties. Because the first and second medium layers 130 and 140 haveinsulating properties, an electric current passes only through theorganic light-emitting layer 40 formed in the defect 120 through thehole transport layer 40 and the electron transport layer 80 when avoltage is applied to the anode 30 and the cathode 50. The materials forthe first medium layer 130 and the second medium layer 140 are limitedinsofar as these two layers can form a photonic band gap by periodicdistribution.

The organic light-emitting layer 40 is embedded into the defect 120. Inthe present embodiment, the defect 120 of the grating 110 also functionsas the light-emitting layer 40. The defect 120 is formed so that theenergy level caused by the vacancy exists inside the emission spectrumof the organic light-emitting layer 40 by the electrically pumping.

The action and the effect of the light-emitting device 42000 will bedescribed below.

Electrons are introduced from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 throughthe hole transport layer 70 into the organic light-emitting layer 40 byapplying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of these electrons and holes. Therefore, light with aremarkably narrow emission spectrum width prescribed by the width of theenergy level caused by the vacancy can be obtained with high efficiencyby the photonic band gap of the grating 110.

(Seventeenth Embodiment)

FIG. 22 is a cross-sectional view schematically showing a light-emittingdevice 43000 according to the present embodiment. The light-emittingdevice 43000 resembles the above-described light-emitting device 42000but differs inasmuch as the hole transport layer is continuously formedwithout forming an insulating layer. The light-emitting device 43000comprises a substrate 10, anode 30, hole transport layer 70, organiclight-emitting layer 40, cathode 50, and grating 110. The anode 30, holetransport layer 70, and cathode 50 are continuously formed.

The grating 110 comprises a defect 120, and the organic light-emittinglayer 40 is formed in this defect 120. A first and second gratings 110 aand 110 b are formed at both sides of the defect 120. These gratings 110a and 110 b can form a photonic band gap to a prescribed wavelengthrange. First medium layers 130 and second medium layers 140 havingdifferent refractive indices are arranged alternately in the gratings110 a and 110 b. The first and second medium layers 130 and 140 standbetween the hole transport layer 70 and the cathode 50. Both the firstand second medium layers 130 and 140 have insulating properties. Becausethe first and second medium layers 130 and 140 have insulatingproperties, an electric current from the cathode 50 passes through theorganic light-emitting layer 40 formed in the defect 120 when a voltageis applied to the anode 30 and the cathode 50. The materials for thefirst medium layer 130 and the second medium layer 140 are limitedinsofar as these two layers can form a photonic band gap by the periodicdistribution.

The organic light-emitting layer 40 is embedded into the defect 120. Inthe present embodiment, the defect 120 of the grating 110 also functionsas the light-emitting layer 40. The defect 120 is formed so that theenergy level caused by the vacancy exists inside the emission spectrumof the organic light-emitting layer 40 by the electrically pumping.

The action and the effect of the light-emitting device 43000 will bedescribed below.

Electrons and holes are introduced into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 through the holetransport layer 70 by applying a prescribed voltage to the anode 30 andthe cathode 50. Excitons are formed in the organic light-emitting layer40 by recombination of these electrons and holes. Therefore, light witha remarkably narrow emission spectrum width prescribed by the width ofthe energy level caused by the vacancy can be obtained with highefficiency by the photonic band gap of the grating 110.

Although an electron transport layer is not formed in this embodiment,an electron transport layer may be formed between the organiclight-emitting layer 40 and the cathode 50. It is unnecessary to formboth the hole transport layer and the electron transport layer. Eitherof these transport layers may be sufficient. This also applies to otherembodiments having a grating constituting a photonic band gap.

(Eighteenth Embodiment)

FIG. 23 is a cross-sectional view schematically showing a light-emittingdevice 44000 according to the present embodiment. The light-emittingdevice 43000 differs from the above-described light-emitting devices41000, 42000, and 43000 inasmuch as the defect and the organiclight-emitting layer are formed in the different areas. Thelight-emitting device 44000 comprises a substrate 10, anode 30, holetransport layer 70, organic light-emitting layer 40, cathode 50, andgrating 110. The anode 30 and the cathode 50 are continuously formed andthe hole transport layer 70 is formed discontinuously.

The grating 110 comprises a defect 120 and first and second gratings 110a and 110 b at each side of the defect 120. These gratings 110 a and 110b can form a photonic band gap to a prescribed wavelength range. Firstmedium layers 130 and second medium layers 140 having differentrefractive indices are arranged alternately in the gratings 110 a and110 b. The defect 120 and the first medium layers 130 are formed by thehole transport layer 70. The second medium layers 140 have insulatingproperties. The materials for the second medium layers 140 are notlimited insofar as the second medium layers 140 can form a photonic bandgap by periodic distribution with the first medium layer 130 whichserves as the hole transport layer 70. The defect 120 is formed so thatthe energy level caused by the vacancy exists inside the emissionspectrum of the organic light-emitting layer 40 by electrically pumping.

The organic light-emitting layer 40 is formed on the hole transportlayer 70 which serves as the defect 120 and stands between the holetransport layer 70 and the cathode 50. In the present embodiment, thedefect 120 of the grating 110 is formed in an area different from thelight-emitting layer 40. Because the defect 120 of the grating 110 alsoserves as the hole transport layer 70 in this embodiment, the organiclight-emitting layer 40 and the defect 120 are formed so that parts ofthem are in contact. An insulating layer 90 is formed between thegrating 110 and the cathode 50 at each side of the organiclight-emitting layer 40.

When a voltage is applied to the anode 30 and the cathode 50, anelectric current from the anode 30 and the cathode 50 is concentrated onthe hole transport layer 70, which also serves as the defect 120, andthe organic light-emitting layer 40 by forming the second medium layers140 having insulation properties and the insulating layer 90.

The action and the effect of the light-emitting device 44000 will bedescribed below.

Electrons and holes are introduced into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 through the holetransport layer 70 by applying a prescribed voltage to the anode 30 andthe cathode 50. Excitons are formed in the organic light-emitting layer40 by recombination of these electrons and holes. Therefore, light witha remarkably narrow emission spectrum width prescribed by the width ofthe energy level caused by the vacancy can be obtained with highefficiency by the photonic band gap of the grating 110.

(Nineteenth Embodiment)

FIG. 24 is a cross-sectional view schematically showing a grating 110 ina light-emitting device 45000 according to the present embodiment. Thisembodiment illustrates a modification of the grating 110. The organiclight-emitting layer 40 is embedded into only the defect 120 of thegrating 110 in the fifteenth to seventeenth embodiments. In thisembodiment, the organic light-emitting layer 40 constitutes not only thedefect 120 but also part of the medium layers of the grating 110. Thesecond medium layers 140 in the area close to the defect 120 are formedby filling in the materials for the organic light-emitting layer 40. Theorganic light-emitting layer can be formed more easily by forming theorganic light-emitting layer 40 over a wider area including the defect120.

The grating 110 comprises a defect 120 and first and second gratings 110a and 110 b at both sides of the defect 120. These gratings 110 a and110 b can form a photonic band gap in a prescribed wavelength range.First medium layers 130, second medium layers 140, and third mediumlayers 150 each having different refractive indices are arrangedalternately in the gratings 110 a and 110 b. The organic light-emittinglayer 40 is formed in the defect 120. The first medium layers 130 andthe second medium layers 140 comprising the organic light-emitting layer40 are arranged alternately near the defect 120, and at both sidesthereof the first medium layers 130 and the third medium layers 150 arearranged alternately. The materials for the first medium layer 130 andthe third medium layer 150 are limited insofar as these at least theselayers can form a photonic band gap by periodic distribution. The defect120 is formed so that the energy level caused by the vacancy existsinside the emission spectrum of the organic light-emitting layer 40 byelectrically pumping.

The grating 110 shown in FIG. 24 is an example of a grating. Thisgrating can be applied to the light-emitting devices according to thefifteenth to seventeenth embodiments as well as light-emitting deviceshaving other configurations.

Among the embodiments described below, the twentieth to twenty-thirdembodiments illustrate the case where an organic light-emitting layerconstitutes a medium layer of a grating.

(Twentieth Embodiment)

FIG. 25 is a cross-sectional view schematically showing a light-emittingdevice 46000 according to the present embodiment. The light-emittingdevice 46000 comprises a substrate 10, anode 30, organic light-emittinglayer 40, cathode 50, and grating 110.

The grating 110 comprises a defect 120 and first and second gratings 110a and 110 b at both sides of the defect 120. These gratings 110 a and110 b can form a photonic band gap to a prescribed wavelength range.First medium layers 130 and a second medium layer 140 having differentrefractive indices are arranged alternately in the gratings 110 a and110 b. The second medium layer 140 is formed of the organiclight-emitting layer 40. The materials for the first medium layers 130are not limited insofar as the first medium layers 130 can form aphotonic band gap by periodic distribution with the second medium layer140.

The organic light-emitting layer 40 is embedded into the defect 120 andthe area where the second medium layers 140 is formed and the upper partthereof are continuous. The defect 120 is formed so that the energylevel caused by the vacancy exists inside the emission spectrum of theorganic light-emitting layer 40 by electrically pumping.

In this embodiment, the organic light-emitting layer 40 functions as thedefect 120 and the second medium layers 140 of the grating 110. Theselayers can be easily formed by continuously forming the organiclight-emitting layer. This also applies to the following twenty-first totwenty-second embodiments.

The action and the effect of the light-emitting device 46000 will bedescribed below.

Electrons and holes are introduced into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 by applying aprescribed voltage to both the anode 30 and the cathode 50. Excitons areformed in the organic light-emitting layer 40 by recombination of theseelectrons and holes. Therefore, light with a remarkably narrow emissionspectrum width prescribed by the width of the energy level caused by thevacancy can be obtained with high efficiency by the photonic band gap ofthe grating 110.

In this embodiment, the anode 30 and cathode 50 may be formed only inthe area corresponding the defect 120 formed from the organiclight-emitting layer 40. The efficiency of current injection into thelight-emitting layer 40 can be improved by forming the electrodes insuch a manner. This also applies to other embodiments having a gratingwhich constitutes a photonic band gap.

(Twenty-first Embodiment)

FIG. 26 is a cross-sectional view schematically showing a light-emittingdevice 47000 according to the present embodiment. The light-emittingdevice 47000 comprises a substrate 10, anode 30, hole transport layer70, organic light-emitting layer 40, electron transport layer 80,cathode 50, and grating 110. The anode 30 and the cathode 50 arecontinuously formed. The hole transport layer 70 and the electrontransport layer 80 are formed discontinuously.

The grating 110 comprises a defect 120 and the organic light-emittinglayer 40 is formed in the defect 120. First and second gratings 110 aand 110 b are formed at both sides of the defect 120. These gratings 110a and 110 b can form a photonic band gap in a prescribed wavelengthrange. First medium layers 130 and second medium layers 140 each ofwhich have a different refractive index are arranged alternately in thegratings 110 a and 110 b. The first medium layers 130 are formed betweenthe anode 30 and the cathode 50. The second medium layers 140 standbetween the hole transport layer 70 and the electron transport layer 80.The first layers 130 has insulating properties. Since the first mediumlayers 130 has insulating properties, when a voltage is applied to theanode 30 and the cathode 50, an electric current flows efficiently intothe organic light-emitting layer 40 formed in the defect 120 through thehole transport layer 40 and the electron transport layer 80. Thematerials for the first medium layers 130 are not limited insofar as thefirst medium layers 130 can form a photonic band gap by periodicdistribution with the second medium layers 140.

The organic light-emitting layer 40 is embedded into the defect 120.Specifically, the defect 120 of the grating 110 also functions as thelight-emitting layer 40 in the present embodiment. The defect 120 isformed so that the energy level caused by the vacancy exists within theemission spectrum of the organic light-emitting layer 40 by electricallypumping.

The action and the effect of the light-emitting device 47000 will bedescribed below.

Electrons are introduced from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 throughthe hole transport layer 70 into the organic light-emitting layer 40 byapplying a prescribed voltage to the anode 30 and the cathode 50.Excitons are formed in the organic light-emitting layer 40 byrecombination of these electrons and holes. Therefore, light with aremarkably narrow emission spectrum width prescribed by the width of theenergy level caused by the vacancy can be obtained with high efficiencyby the photonic band gap of the grating 110.

The following twenty-second and twenty-third embodiments illustrate thecase where one of the medium layers constituting a photonic band gap isan organic light-emitting layer and a defect is formed by a layer otherthan the organic light-emitting layer.

(Twenty-second Embodiment)

FIG. 27 is a cross-sectional view schematically showing a light-emittingdevice 48000 according to the present embodiment. The light-emittingdevice 48000 comprises a substrate 10, anode 30, organic light-emittinglayer 40, electron transport layer 80, cathode 50, and grating 110. Theanode 30, organic light-emitting layer 40, electron transport layer 80,and cathode 50 are continuously formed.

The grating 110 comprises a defect 120 and the electron transport layer80 is embedded into this defect 120. First and second gratings 110 a and110 b are formed at each side of the defect 120. These gratings 110 aand 110 b can form a photonic band gap in a prescribed wavelength range.First medium layers 130 and second medium layers 140, each of which havea different refractive index, are arranged alternately in the gratings110 a and 110 b. The first medium layers 130 are formed from the organiclight-emitting layer 40. The second medium layers 140 are formed fromthe electron transport layer 80. The materials for the first mediumlayer 130 and the second medium layer 140 are not limited insofar asthese materials can function as the organic light-emitting layer and theelectron transport layer and form a photonic band gap by periodicdistribution of both materials.

The organic light-emitting layer 40 is formed below the electrontransport layer 80 which serves as the defect 120 and stands between theelectron transport layer 80 and the anode 30. In the present embodiment,the defect 120 of the grating 110 is formed in an area differing fromthe light-emitting layer 40. Since the defect 120 of the grating 110also serves as the electron transport layer 80 in this embodiment, theorganic light-emitting layer 40 and the defect 120 are formed so as tobe in contact in a certain area. The defect 120 is formed so that theenergy level caused by the vacancy exists within the emission spectrumof the organic light-emitting layer 40 by electrically pumping.

The action and the effect of the light-emitting device 48000 will bedescribed below.

Electrons are introduced from the cathode 50 through the electrontransport layer 80 and holes are introduced from the anode 30 into theorganic light-emitting layer 40 by applying a prescribed voltage to theanode 30 and the cathode 50. Excitons are formed in the organiclight-emitting layer 40 by recombination of these electrons and holes.Therefore, light with a remarkably narrow emission spectrum widthprescribed by the width of the energy level caused by the vacancy can beobtained with high efficiency by the photonic band gap of the grating110.

(Twenty-third Embodiment)

FIG. 28 is a cross-sectional view schematically showing a light-emittingdevice 49000 according to the present embodiment. The light-emittingdevice 49000 comprises a substrate 10, anode 30, hole transport layer70, organic light-emitting layer 40, cathode 50, and grating 110. Theanode 30 and the cathode 50 are continuously formed. The hole transportlayer 70 and the organic light-emitting layer 40 are formeddiscontinuously.

The grating 110 comprises a defect 120 and the defect 120 is formed fromthe materials which constitute a first medium layer 130. First andsecond gratings 110 a and 110 b are formed at each side of the defect120. These gratings 110 a and 110 b can form a photonic band gap in aprescribed wavelength range. The first medium layers 130 and secondmedium layers 140, each of which have a different refractive index, arearranged alternately in the gratings 110 a and 110 b. The first mediumlayers 130 are formed between the anode 30 and the cathode 50. Thesecond medium layers 140 stand between the hole transport layer 70 andthe cathode 50. The first medium layers 130 have insulating properties.Since the first medium layers 130 have insulating properties, anelectric current is efficiently introduced into only the organiclight-emitting layers 40 which constitute the second medium layers 140through the hole transport layer 70 when a voltage is applied to theanode 30 and the cathode 50. The materials for the first medium layers130 are not limited insofar as the first medium layers 130 can form aphotonic band gap by periodic distribution with the second medium layers140.

The organic light-emitting layers 40 serve as the second medium layers140 and stand between the hole transport layer 70 and the cathode 50.The defect 120 serves as the first medium layer 130. Specifically, thedefect 120 of the grating 110 of the present embodiment is formed in anarea differing from the light-emitting layer 40. The defect 120 isformed so that the energy level caused by the vacancy exists within theemission spectrum of the organic light-emitting layer 40 by electricallypumping.

The action and the effect of the light-emitting device 49000 will bedescribed below.

Electrons and holes are introduced into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 through the holetransport layer 70 by applying a prescribed voltage to the anode 30 andthe cathode 50. Excitons are formed in the organic light-emitting layer40 by recombination of these electrons and holes. Therefore, light witha remarkably narrow emission spectrum width prescribed by the width ofthe energy level caused by the vacancy can be obtained with highefficiency by the photonic band gap of the grating 110.

The following twenty-fourth embodiment illustrates the case where anorganic light-emitting layer is formed by a layer different from agrating.

(Twenty-fourth Embodiment)

FIG. 29 is a cross-sectional view schematically showing a light-emittingdevice 50000 according to the present embodiment. The light-emittingdevice 50000 comprises a substrate 10, anode 30, hole transport layer70, organic light-emitting layer 40, cathode 50, and grating 110. Theanode 30, organic light-emitting layer 40, and cathode 50 arecontinuously formed. The hole transport layer 70 is formeddiscontinuously.

The grating 110 comprises a defect 120 and first and second gratings 110a and 110 b at each side of the defect 120. These gratings 110 a and 110b can form a photonic band gap in a prescribed wavelength range. Thefirst medium layers 130 and second medium layers 140, each of which havea different refractive index, are arranged alternately in 5 the gratings110 a and 110 b. The defect 120 and the first medium layer 130 areformed by the hole transport layer 70. The second medium layer 140 hasinsulating properties. The materials for the second medium layers 140are not limited insofar as the second medium layers 140 can form aphotonic band gap by periodic distribution with the first medium layer130 which serves as the hole transport layer 70. The defect 120 isformed so that the energy level caused by the vacancy exists within theemission spectrum of the organic light-emitting layer 40 by electricallypumping.

The organic light-emitting layer 40 is formed on the hole transportlayer 70 which serves as the defect 120 and stands between the grating110 and the cathode 50. Specifically, the defect 120, of the grating 110of the present embodiment is formed in an area differing from theorganic light-emitting layer 40.

The action and the effect of the light-emitting device 50000 will bedescribed below.

Electrons and holes are introduced into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 through the hole,transport layer 70 by applying a prescribed voltage to the anode 30 andthe cathode 50. Excitons are formed in the organic light-emitting layer40 by recombination of these electrons and holes. Therefore, light witha remarkably narrow emission spectrum width prescribed by the width ofthe energy level caused by the vacancy can be obtained with highefficiency by the photonic band gap of the grating 110.

(Twenty-fifth Embodiment)

FIG. 30 is a cross-sectional view schematically showing a light-emittingdevice 51000 according to the present embodiment. In the light-emittingdevice 51000, a grating is formed in the direction different from thatin the above-described embodiments. The light-emitting device 51000comprises a substrate 10, anode 30, organic light-emitting layer 40,cathode 50, and grating 110. The grating 110 is formed perpendicular tothe substrate 10.

The grating 110 comprises a defect 120 and first and second gratings 110a and 110 b at each side of the defect 120. These gratings 110 a and 110b can form a photonic band gap in a prescribed wavelength range. Thefirst medium layers 130 and second medium layers 140, each of which havea different refractive index, are arranged alternately in the gratings110 a and 110 b. The first medium layers 130 are formed by the organiclight-emitting layer 40. The materials for the second medium layers 140are not limited insofar as the second medium layers 140 can form aphotonic band gap by periodic distribution with the first medium layer130.

The organic light-emitting layer 40 is embedded into the defect 120.Specifically, the defect 120 of the grating 110 also functions as thelight-emitting layer 40 in the present embodiment. The defect 120 isformed so that the energy level caused by the vacancy exists within theemission spectrum of the organic light-emitting layer 40 by electricallypumping.

The anode 30 and the cathode 50 are formed perpendicular to thesubstrate 10.

The action and the effect of the light-emitting device 51000 will bedescribed below.

Electrons and holes are introduced into the organic light-emitting layer40 respectively from the cathode 50 and the anode 30 by applying aprescribed voltage to both the anode 30 and the cathode 50. Excitons areformed in the organic light-emitting layer 40 by recombination of theseelectrons and holes. Therefore, light with a remarkably narrow emissionspectrum width prescribed by the width of the energy level caused by thevacancy can be obtained with high efficiency by the photonic band gap ofthe grating 110.

The present invention is not limited to the above-described embodimentsand many modifications and variations are possible within the scope ofthe present invention.

For example, some of the above embodiments comprise a pair of claddinglayers. However, if other layers such as the electrode layer made frommetals can confine light, the cladding layers may be omitted. Moreover,the above embodiments illustrate light-emitting devices comprising anorganic light-emitting layer as a light-emitting layer. A light-emittinglayer comprising inorganic materials may be used instead of such anorganic light-emitting layer.

As described above, the present invention can provide a light-emittingdevice with a narrow spectral width of emission wavelength and excellentdirectivity.

What is claimed is:
 1. A light-emitting device comprising: a firstcladding layer; a first electrode layer formed above the first claddinglayer; a light-emitting layer that emits light by electroluminescenceand formed above the first electrode layer; a second electrode layerformed above the light-emitting layer; a second cladding layer formedabove the second electrode layers; and a grating formed further insidebetween the first and second cladding layer.
 2. The light-emittingdevice according to claim 1 further comprising: a core layer formedbetween the first cladding layer and the first electrode layer, whereinthe grating is formed in the core layer.
 3. The light-emitting deviceaccording to claim 1 further comprising: a core layer formed between thefirst cladding layer and the first electrode layer, wherein the gratingis formed at a boundary area between the core layer and the firstcladding layer.
 4. The light-emitting device according to claim 1further comprising: at least one of a first transport layer formedbetween the light-emitting layer and the first electrode layer and asecond transport layer being formed between the light-emitting layer andthe second electrode layer.
 5. The light-emitting device according toclaim 4, wherein the grating is formed in one of the first and secondtransport layers.
 6. The light-emitting device according to claim 4,wherein the grating is formed at a boundary area between one of theadjacent first and second transport layers and one of the first andsecond electrode layers.
 7. The light-emitting device according to claim4, wherein the grating is formed at a boundary area between the firsttransport layer or second transport layer and the light-emitting layer.8. The light-emitting device according to claim 1, wherein thelight-emitting layer constitutes one medium of the grating and is formedby layers that are discontinuously arranged.
 9. The light-emittingdevice according to claim 8, wherein the grating is formed by thelight-emitting layer and one of the first and second transport layers.10. The light-emitting device according to claim 8, wherein the gratingis formed by the light-emitting layer and one of the first and secondelectrode layers.
 11. The light-emitting device according to claim 8,wherein the grating is formed by the light-emitting layer and aninsulating medium layer.
 12. A light-emitting device comprising: acladding layer; a first electrode layer formed above the cladding layer;a light-emitting layer that emits light by electroluminescence andformed above the first electrode layer; a second electrode layer formedabove the light-emitting layer; and a grating formed further insidebetween the cladding layer and the second electrode layer.
 13. Thelight-emitting device according to claim 12, wherein the secondelectrode layer is a cathode.
 14. The light emitting device according toclaim 12, further comprising: at least one of a first transport layerbeing formed between the light-emitting layer and the first electrodelayer and a second transport layer being formed between thelight-emitting layer and the second electrode layer.
 15. Thelight-emitting device according to claim 14, wherein the grating isformed by the light-emitting layer and first transport layer or secondtransport layer.
 16. A light-emitting device comprising: a claddinglayer; a first electrode layer formed above the cladding layer; a lightemitting layer that emits light by electroluminescence and formed partlyabove the first electrode layer; a second electrode layer formed abovethe light-emitting layer; at least one of a first transport layer formedbetween the light-emitting layer and the first electrode layer and asecond transport layer formed between the light-emitting layer and thesecond electrode layer; and a grating formed further inside between thecladding layer and the second electrode layer.
 17. The light-emittingdevice according to claim 16, wherein the light-emitting layer is formedin a concave portion of one of the first and second transport layers,and wherein the grating is formed by the one of the first and secondtransport layers and air.
 18. The light-emitting device according toclaim 16, wherein the grating is formed by one of the first and secondtransport layers and an insulating medium layer.
 19. A light-emittingdevice comprising: an EL element section in which a plurality of layersare formed in concentric circles; an optical fiber section; wherein theEL element section comprises: a first core layer; a first electrodelayer formed at an exterior of the first core layer; a light-emittinglayer that emits light by electroluminescence and formed at an exteriorof the first electrode layer; a second electrode layer formed at anexterior of the light-emitting layer; a first cladding layer formed atan exterior of the second electrode layer; a grating formed in the firstcore layer, wherein the optical fiber section comprises: a second corelayer; and a second cladding layer formed at an exterior of the secondcore layer, wherein the first core layer of the EL element section andthe second core layer of the optical fiber section are formed on anidentical axis.
 20. The light-emitting device according to claim 19,wherein the first core layer comprises first medium layers and secondmedium layers each of which is provided alternately, and wherein thegrating is formed by the first and second medium layers.
 21. Thelight-emitting device according to claim 19, wherein the first andsecond core layers continue integrally, and wherein the grating isformed by the first core layer and the first electrode layer.
 22. Thelight-emitting device according to claim 19, wherein the first andsecond core layers continue integrally, and wherein the grating isformed by the first electrode layer and a medium layer.
 23. Alight-emitting device comprising: an EL element section; and an opticalfiber section, wherein the EL element section comprises: a first corelayer having a plane surface; a first electrode layer being formed abovethe plane surface of the first core layer; a light-emitting layer thatemits light by electroluminescence and formed above the first electrodelayer; a second electrode layer formed above the light-emitting layer; afirst cladding layer formed at an exterior of the first core layer; asecond cladding layer formed at an exterior of the first electrodelayer, the light-emitting layer and the second electrode layer; and agrating formed in the first core layer, wherein the optical fibersection comprises: a second core layer; and a third cladding layerformed at an exterior of the second core layer, wherein the first corelayer of the EL element section and the second core layer of the opticalfiber section are formed on an identical axis.
 24. The light-emittingdevice according to claim 23, wherein the first core layer comprisesfirst and second medium layers provided alternately, and wherein thegrating is formed by the first and second medium layers.
 25. Alight-emitting device comprising: a substrate; a first electrode layerformed above the substrate; an organic light-emitting layer that emitslight by current excitation and formed above the first electrode layer;a second electrode layer formed above the organic light-emitting layer;and a grating formed further inside between the substrate and the secondelectrode layer, wherein the grating has: a one-dimensional periodicrefractive index distribution which constitutes a photonic band gap; anda defect which is designed so that the energy level caused by a vacancyis within a specific emission spectrum.
 26. The light-emitting deviceaccording to claim 25 further comprising: at least one of a firsttransport layer formed between the organic light-emitting layer and thefirst electrode layer and a second transport layer formed between theorganic light-emitting layer and the second electrode layer.
 27. Thelight-emitting device according to claim 26, wherein the organiclight-emitting layer is formed in a concave portion of one of the firstand second transport layers and constitutes the defect, and wherein thegrating is formed by a medium layer and one of the first and secondtransport layers.
 28. The light-emitting device according to claim 26,wherein the organic light-emitting layer is formed between the first andsecond transport layers and constitutes the defect, and wherein thegrating is formed by first and second medium layers.
 29. Thelight-emitting device according to claim 26, wherein the organiclight-emitting layer is formed between one of the adjacent first andsecond transport layers and one of the first and second electrode layersand constitutes the defect, and wherein the grating is formed by firstand second medium layers.
 30. The light-emitting device according toclaim 26, wherein the organic light-emitting layer is formed between oneof the adjacent first and second transport layers and one of the firstand second electrode layers, and wherein the grating is formed by firstand second medium layers and the defect is formed by one of the firstand second medium layers.
 31. The light-emitting device according toclaim 25, wherein the organic light-emitting layer constitutes thedefect, wherein the grating near the defect constitutes one of first andsecond medium layers formed from a same material as the organiclight-emitting layer, and wherein other parts of the grating are formedby the first and second medium layers.
 32. The light-emitting deviceaccording to claim 25, wherein the grating is formed by the organiclight-emitting layer and a medium layer.
 33. The light-emitting deviceaccording to claim 26, wherein the grating is formed by the organiclight-emitting layer and one of the first and second transport layers.34. The light-emitting device according to claim 25, wherein the gratingis formed by the organic light-emitting layer and a medium layer, andwherein the defect is formed by the medium layer.
 35. The light-emittingdevice according to claim 26, wherein the grating is formed by a mediumlayer and one of the first and second transport layers, and wherein thedefect is formed by the medium layer.
 36. A light-emitting devicecomprising: a substrate; a first grating formed above the substrate; anorganic light-emitting layer that emits light by current excitation andformed above the first grating; a second grating formed above theorganic light-emitting layer; and first and second electrode layersformed at either ends of the first grating, the organic light-emittinglayer and the second grating, wherein the first and second gratingshave: a one-dimensional periodic refractive index distribution whichconstitutes photonic band gap; and a defect which is designed so thatthe energy level caused by a vacancy is within a specific emissionspectrum.
 37. The light-emitting device according to claim 36, whereinthe organic light-emitting layer constitutes the defect, and wherein thefirst and second gratings are formed by the organic light-emitting layerand a medium layer.